This invention relates generally to electrical current sensing arrangements and is particularly directed to the mounting and electrical coupling of a toroidally wound current pick-up coil.
One approach to detecting the current in a conductor is to position a magnetic field responsive coil adjacent to the conductor and measure current flow therein in response to changes in the magnetic field arising from current changes in the conductor. The pick-up coil frequently takes the form of a toroidally wound wire disposed around a donut-shaped ferrite core with the current carrying conductor passed through the ferrite core's aperture. This arrangement is particularly useful for detecting current pulses in the conductor.
A typical prior art current sensor arrangement incorporating a toroidally wound pick-up coil is shown in FIG. 1. The toroidally wound pick-up coil 10 is wrapped around a donut-shaped ferrite core 12. The combination of the toroidal coil 10 and ferrite core 12 is affixed to a support structure 18 which in FIG. 1 is represented as a transformer 18 by means of a hot melt epoxy cement 24. Disposed within the aperture in the toroidal coil and ferrite core combination may be one or more conductors within which it is desired to detect a current or current pulses. In FIG. 1, a first plurality of conductors 15 are shown disposed within a first insulating sheath 16 which is positioned within the aperture of the toroidal coil/ferrite core combination. A second sheath 22 within which may be disposed one or more windings of a choke 20 is also shown positioned within the toroidal coil 10. Changes in the magnetic flux arising from current variations within any of the aforementioned conductors or leads is sensed by the toroidal coil and ferrite core combination resulting in an electromagnetic potential being applied across the toroidal coil and a current induced therein. A pair of leads 17 extending from the toroidal coil 10 carries a current which represents the change in current within any of the conductors positioned within the toroidal coil and permits this current change to be detected and measured by conventional means which are not shown in FIG. 1.
The arrangement of FIG. 1 suffers from various limitations. For example, the conductors must be manually inserted through the combination of the toroidal coil 10 and ferrite core 12 and must then be coupled to associated circuitry. The toroidal coil/ferrite core combination must then be affixed to the conductors by means of the epoxy cement in a procedure which is inherently imprecise in terms of the positioning of the toroidal coil along the length of the conductors and with respect to other adjacent electronic components which may provide an unwanted magnetic field input to the pick-up coil. In addition, the positioning and mounting of the toroidal pick-up coil must be performed manually and thus represents a labor intensive, rather expensive approach. Moreover, manual application of the hot melt epoxy cement tends to be messy and imprecise. Finally, should the need arise to later replace the toroidal pick-up coil, the mounting arrangement of FIG. 1 is particularly undesirable since the pick-up coil has been more or less permanently affixed to its support structure.
The present invention is intended to overcome the aforementioned limitations of the prior art by providing a current sensor arrangement employing a toroidally wound pick-up coil which is positioned upon a mounting/connecting block or interface housing in a manner which ensures its secure mounting upon and electrical connection to a printed circuit (PC) board while providing for the automatic insertion within the pick-up coil of the conductor or conductors in which the current is to be detected.